1. Field of the Invention
This invention relates to a process for the preparation of cyano-substituted carboxylic acid esters by reacting an acid halide, an aromatic aldehyde and a water-soluble cyanide.
2. Description of the Prior Art
A valuable group of esters consists of pesticides of the pyrethrin type, particularly those .alpha.-cyano esters as described in U.S. Pat. Nos. 3,835,176 and 3,996,244 and 4,024,163. These so-called synthetic pyrethroids have exceptionally good insecticidal and acaricidal properties while possessing a very low mammalian toxicity. This combination of properties makes these .alpha.-cyano esters of considerable interest to the agrochemical industry and much effort has been devoted to finding economic routes to these "synthetic pyrethroids".
U.S. Pat. Nos. 4,110,360-3 and 4,123,451 disclose the preparation of .alpha.-cyano esters from an acid halide, an aldehyde and a water-soluble cyanide. The present application is an improvement thereto.